Wilo Solar-STG 15/11-1 Drainback Circulator Pump

Wilo Solar-STG 15/11-1 Drainback Circulator Pump

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Replaces the Salmson HXE 63-15 P circulating pump used in Rheem and Solahart drainback systems, and suits most other drainback systems. Wilo article 4061442, type Star-STG 15/11.

What a drainback system needs, and why this pump is different

In a drainback system the solar fluid empties back into a reservoir every time the pump stops, so nothing is left up in the collectors to freeze in winter or boil in summer. When the pump restarts it has to lift the entire column of fluid back up to the roof before circulation begins.

That takes far more work than simply circulating fluid around a loop already full. This pump draws up to 165 W, where an open loop solar circulator such as the Wilo Star-Z NOVA draws about 5 W. A standard solar circulator will not refill a drainback system — it does not have the head to lift the fluid, and the system will never start.

Drainback is a third arrangement, separate from open loop and closed loop. If you are not certain which you have, the reservoir is the giveaway: a drainback system has a small tank that the fluid falls back into when the pump stops.

Will this pump fit my system?

Fit is decided by the pump's dimensions and duty, not by the brand on the tank:

• Port-to-port: 180 mm thread to thread, with G 1 union nuts. Measure your existing pump face to face — if it is 180 mm, this is a direct replacement.
• Three speeds: 75 / 115 / 165 W. Set the speed to match the lift your system needs. More speed is not better — the lowest setting that reliably refills the collectors is the one to use.
• Drainback and closed loop only. Not for open loop potable water. The housing is grey cast iron, which corrodes in oxygenated drinking water. If the water from your taps passes through the pump, you need the brass Wilo Star-Z NOVA instead.
• Approved fluids: heating water to VDI 2035, and water-glycol mixtures to a maximum of 1:1. Above 20% glycol the pumping data must be re-checked.
• Minimum suction head at the suction port, to avoid cavitation: 0.5 m at 50 °C, 3 m at 95 °C, 10 m at 110 °C.

Not sure what you have? Email a photo of your existing pump and of the reservoir to sales@solarhotwaterparts.com.au and we will confirm the right part before you buy.

Technical data

Installation and licensing

This product is new and supplied in the original packaging, subject to the manufacturer's warranty and to consumer guarantees under the Australian Consumer Law.

It must be installed by a licensed tradesperson as required by law. Failure to do so breaches the manufacturer's warranty, may result in injury or death, may jeopardise your insurance and may breach the relevant legislation. Check with your local authority for the licensing requirements that apply to plumbing and electrical work in your state.

*All images used in this listing are for illustrative purposes only.